Heading aims: Dihydromyricetin (DMY) is the most abundant ingredient in vine tea. Here, we investigated the cytoprotective effects and possible mechanisms of DMY on hydrogen peroxide (H2O2)-induced oxidative stress damage in human umbilical vein endothelial cells (HUVECs). Materials and methods: The percentage of cell viability was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MU) assay. We determined the antioxidant properties of DMY by measuring the activity of superoxide dismutase (SOD) and malondialdehyde (MDA). Flow cytometry was used to measure apoptosis in HUVECs that were double stained with Hoechst 33342 and propidium iodide (PI). The generation of intracellular reactive oxygen species (ROS) was measured in 2',7'-dichlorofluorescin diacetate (DCFH-DA)-loaded HUVECs using a fluorescent microscope. Moreover, the expression of apoptosis-related proteins was determined by Western blotting. In addition, the release of nitric oxide (NO) was analyzed using a commercial kit. Key findings: HUVECs treated with H2O2 had a notable decrease in cell viability that was attenuated when cells were pretreated with DMY (37.5-300 mu M). DMY pretreatment significantly attenuated H2O2-induced apoptosis in HUVECs and inhibited intracellular ROS overproduction. Finally, pretreatment of cells with DMY prior to H2O2 exposure resulted in the inhibition of p53 activation, followed by the regulation of the expression of Bcl-2 and Bax, the release of cytochrome c, the cleavage (activation) of caspase-9 and caspase-3, and then the suppression of PARP cleavage in H2O2-induced HUVECs. Significance: Our study is the first to report that DMY can protect HUVECs from oxidative stress damage, an effect that is mediated by the mitochondrial apoptotic pathways. (C) 2015 Elsevier Inc. All rights reserved.